Vision Enhancement System (Bausch & Lomb, Rochester, New York),were measured. Also tested were older models from same threemanufacturers. After each system was primed using Balanced SaltSolution (BSS), the aspiration line was connected to an electronicpressure transducer and digital oscilloscope. Small volumes of fluid wereinjected and aspirated from the aspiration line to generate pressure-volume curves for each consumable pack.

Results:Under controlled laboratory settings, the INFINITI system withIntrepid tubing demonstrated the lowest compliance while the Legacyproved to be the most compliant. The AMO and Bausch and Lombsystems exhibited very similar pressure-volume curves.

used in cataract surgery account for a largeportion of their performance and safety profiles.

A system’s compliance is a measure of its abilityto expand or contract in response to applied fluidicpressure.

Compliance, which is the inverse of stiffness, isdefined as ∆volume/∆pressure.

In phacoemulsification systems, aspiration linecompliance is a function of the mechanicalproperties of the aspiration tubing and thecassette that mates with the pump mechanism.

When the tip of a phacoemulsification or irrigation–aspirationprobe becomes occluded, the pump stops turning once thesystem senses that vacuum limit has been reached.

Variable amounts of potential energy are stored in the walls ofthe tubing and cassette depending on the compliance of thesecomponents and the vacuum limit set by the surgeon.

Vacuum is useful for holding onto and aspirating solid lensfragments, but occlusion break can cause problems when ithappens under high vacuum.

At occlusion break, the potential energy stored in the tubing andcassette suddenly releases, causing a sudden suctioning of fluidfrom the eye to fill the recoiled volume.

The anterior chamber collapses in response to the sudden lossof volume, risking damage to the cornea, iris, or lens capsule.

Occlusion break surge might possibly be eliminated ifphacoemulsification systems could be designed that had zerocompliance.

In a previous experiment, we demonstrated a measurabledifference in occlusion surge between the 3 leadingmanufacturer's newest phacoemulsification systems. Atequivalent vacuum limits, the primary determinant of surgeamplitude is the system compliance.

As a next logical step in our studies, we decided to measurethe compliance of the new and oldphacoemulsifiers

fromAlcon, AMO and Bausch & Lomb.

Systems Studied:

Bauschand Lomb:

Stellaris

Vision Enhancement system

MillenniumMicorsurgical

system

Alcon Laboratories Inc:

INFINITI Vision system (both Intrepid

and Standard tubing)

Advantec

Legacy

Abbot Medical Optics:

WhiteStar

Signiture

Whitestar

Sovereign

Before measuring compliance, cassettes (phaco

packs) were loaded intoeach of the 6phacoemulsifiers

and the devices were primed withbalanced salt solution, taking care to eliminate all air bubbles.

An electronic pressure transducer was connected to a power supply and adigital storage oscilloscope. The irrigation line, aspiration line, and a 1mlU-1100 latex free insulin syringe were connected to the transducer. Thepressure transducer was placed at the same height as the vacuum sensorin the cassette of the machine under test.

(a net withdrawal of 0.40mL), recording the line pressure ateach point. The process was also reversed to test for hysteresis.

Compliance curves were generated for 3 cassettes perphacoemulsifier

and averaged. In addition, 1 cassette per instrument was tested 3 times tolook for fatigue, which is a change in compliance with repeated testing. Alltesting was done on the same day to minimize variability due toatmospheric and temperature conditions.

•Additionally, the capacitance ofone cassette from each systemwas measured. The volume heldin the aspiration tubing until thevery edge of the cassette wasrecorded as well as the volumeneeded to fill half of the pumptubing in the cassette and thevolume needed to obtain onedrop of fluid in the bag.

Figure 1: Compliancecurve for all six systems, in addition to the Infiniti standard tubing.Asteeper slope indicates a lower compliance.

The 7 cassettes that were tested demonstrated similar compliancecurves under negative and positive pressure loading. Compliance curvesfor all systems were reproducible between three different cassettes andbetween three trials on one cassette. The Infiniti Intrepid tubingdemonstrated the least compliance (steepest curve) for both the averageof three cassettes and three runs on one cassette. The LegacyAdvantec

systems had less pronounced compliance difference as compared to theprevious generation units, the Sovereign and theMillenium, respectively.

All six systems demonstrated a hysteresis when compliance curvesobtained by aspirating fluid and compliance curves obtained byinjecting fluid were compared. The curves for the newer models areshown above.

The Alcon Infiniti standard and Infiniti Intrepid packs had three to four timesthe fluid capacity of the other systems when comparing the capacitancefrom the tip of the aspiration line to the bag because of an extra fluidchamber held in the cassette. Since this chamber is filled after fluid haspassed the pump, this volume should not contribute to the compliance ofthe tubing.

Comparing the capacitance of the tubing half way through the pumpreveals that the Infiniti Intrepid and Infiniti standard packs have acapacitance of 9.1 and 9.5 ml, respectively, compared to 5.3mL

for theSignature and 7.5mL

for theStellaris

.

The phacoemulsification system that has the lowest occlusionbreak surge allows for the most effective and safest procedure.



Since occlusion break surge is largely determined by the tubing’scompliance, the same can be said for the system which is theleast compliant.

Our results illustrate improvements in the fluidics of the newerphacoemulsification systems by all three major manufacturers.



Our study demonstrates that the Infiniti Intrepid tubing is the leastcompliant and therefore should provide the best clinicalperformance.